Geographical variation in metacercarial infection levels in marine invertebrate hosts: parasite species character versus local factors |
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Authors: | David W Thieltges Brian L Fredensborg Robert Poulin |
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Institution: | (1) Department of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand;(2) Department of Biology, University of Texas-Pan American, 1201 W University Drive, Edinburg, TX 78539, USA |
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Abstract: | Despite the important roles played by parasites in local population dynamics and community structure of marine ecosystems,
there is a lack of information on the geographical variation in infection levels displayed by particular host–parasite species
combinations. This study examines geographical variation in infection levels by the metacercarial stages of trematode parasites
in crustacean and bivalve second intermediate hosts. Analyses were based on a dataset compiled from the literature, consisting
of 164 local samples representing 49 host–parasite species pairs for crustaceans, and 338 entries representing 36 host–parasite
species pairs for bivalves. The analyses indicate that for all measures of infection levels prevalence (percentage of individuals
infected), intensity (mean no. of metacercariae per infected individual), abundance (mean no. of metacercariae across all
individuals in a sample)], there was statistically significant repeatability of infection values within host–parasite species
pairs. However, it is only for values of intensity and abundance of infection in crustacean hosts that the repeatability was
strong; this suggests that infection levels are specific properties of crustacean–trematode species pairs, showing significant
consistency across localities despite spatial variation in abiotic and biotic conditions. Although the magnitude of variation
in infection levels within parasite species pairs (measured as coefficients of variation) was independent of scale in crustacean
hosts, infection levels in bivalves increased in variability at large (>100 km) spatial scales. These results suggest that
there is a considerable geographical consistency in parasite load, especially in crustacean hosts, which should lead to consistent
ecological and ecosystem effects of marine trematodes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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